Pneumatic tacker



May 31, 1960 H. LERNER PNEUMATIC TACKER Filed April 20, 1953 12 Sheets-Sheet 1 INVENTOR HERSHf Y LEE/V51? ATTORNEY H. LERNER PNEUMATIC TACKER May 31, 1960 12 Sheets-Sheet 2 Filed April 20, 1953 INVENTOR m N m Y Z W Y m H T 3 T M A ml 0 4 M6 M m 6 MN 7 55 N 6 m. 4 9 6 9 7 \HQ b 2 m L mm L y 31, 1960 H. LERNER 2,938,212

PNEUMATIC TACKER Filed April 20. 1953 12 Sheets-Sheet 3 B /40 INVENTOR HERSHEY tf/FWAA? 4 ATTORNEY May 31, 1960 H. LERNER PNEUMATIC TACKER 12 Sheets-Sheet 5 Filed April 20. 1953 1 m H h d M H l 2 M s ii, i w. a It! 1 P /.7A./ M7 6 w .M 5 mm wm M INVENTOR HERSHfY AER/Vt")? ATTORNEY May 31, 1960 H. LERNER 2,938,212

PNEUMATIC TACKER INVENTOR HERSHFY Zf/P/Vf/P ATTORNEY May 31, 1960 H. LERNER PNEUMATIC TACKER l2 Sheets-Sheet 7 Filed April 20, 1953 m 1, P B w M a m r W p e w E w e w NVENTOR 51 53 M6 Hf/iSHE) LEE/V51? 54 BY ATTORNEY invllll.

May 31, 1960 Filed April 20, 1953 l2 Sheets-Sheet 8 lI/l/ll INVENTOR HERSHEY LEFPNE/P mew/- ATTORN EY y 1, 1960 H. LERNER 2,938,212

- PNEUMATIC TACKER Filed p il 20. 1953 12 Sheets-Sheet 9 INVENTO R HERSHEY LE F/VEH ATTORNEY k May 31, 1960 H. LERNER PNEUMATIC TACKER l2 Sheets-Sheet 1O filed April 20, 1953 I I b ll V V ,W/

INVENTOR fw 0 4 1 m W 4 $1 7 $5 a We J6EE W W U ATTORNEY May 31, 1960 H. LERNER 2,938,212

PNEUMATIC TACKER Filed April 20, 1953 12 Sheets-Sheet 11 1 9 [1/6) /33 :2 W Ill J00 I (b 5i Q p2? *M 57' I I33 195/ I /3/ HERSHEY LERNEI? J7 BY 4 k C}? 5 96 98 ATTORNEY May 31, 1960 H. LERNER PNEUMATIC TACKER l2 Sheets-Sheet 12 Filed April 20, 1953 INVENTOR HERSHEY LEE/V55 L I. I

ATTO R N EY United States Patent 7 2,938,212 PNEUMATIC TACKER Hershey Lerner, Bayside, N.Y., assignor, by mesne assignments, to Inventions Management Corporation, Raleigh, N.C., a corporation of North Carohna Filed Apr. 20, 1953, Ser. No. 349,852 94 Claims. (Cl. 144.4)

The subject matter of this invention is a stapling machine and more specifically is concerned with a functionally and structurally improved pneumatic tacker. One important object of the invention is concerned with a highly serviceable tacker which can conveniently hold at least five thousand staple elements in close compact fashion in the form of a roll in a small container utilized as a disposable cartridge which is easy to load on and into the tacker and which is easy to unload when the staple element roll is used up. Another important object is to provide a novel pneumatic tacker which is easy to manufacture to the end that the parts thereof do not require close tolerances. Specifically another object resides in the provision of a novel tacker requiring no special skill for its effectiveness in respect to eflicient operation and the staple driving means thereof is independent of the rate of speed of actuation of the trigger controlling the admission of air pressure into the cylinder of the tacker. A further specific object is realized in the provision of a tacker which can be cornered, namely, the staple ejected can be driven into right angle corners by reason of the acute angle formed by the cylinder and the base or case of the tacker, thus permitting automatic positioning of the staple raceway of the tacker into the corner while the cylinder thereof is appreciably spaced from a wall forming in part the corner and even such corner positioning can take place while the former and driving blades are located along the center line of the forming and driving pistons within the cylinder. A further particular object is concerned with a tacker wherein the staple raceway is formed by separable parts adapted to be swung apart for prompt access thereto and consequently adapted for easy cleaning. Another object is to employ in the disposable cartridge a foldable and flexible belt in the form of a roll of rectilinear and resiliently connected wire elements with the foremost element thereof adapted to be successively fed over the forward or anvil end of a linearly guided bending block and subsequently bent against the sides of the anvil end of the bending block to form an inverted U shaped staple after which the formed staple is driven out of the tacker. Another object is to form the U shaped staple from the foremost rectilinear wire element of the resilient and flexible staple element strip issuing from the roll in the first part of the down stroke of a pneumatically actuated compound piston of the tacker and subsequently drive on the remaining part of this same downstroke the formed staple out of the tacker and into the material to be fastened. Another object resides in providing the compound piston with a channel shaped former to bend the foremost wire element of the staple element strip over the slidably guided bending block, and with a driving blade for subsequently forcing and ejecting the formed staple out of the raceway of the tacker. Another object is to operate the driving blade at a high rate of speed, consequently reducing the recoil of the tacker. Another specific object is to expose the staple driving piston to predetermined maximum air pressure pursuant to the full stroke of the forming piston, thus insuring full benefit of the maximum pressure desired on the driving piston irrespective of the time utilized in manipulating the trigger for initiating admission of air into the forming piston. Another object is to provide an effective staple element belt feeding means for presenting the foremost staple element of the staple element strip over the front anvil part of the slidable but spring controlled bending block after each complete cycle of the compound piston, namely, a cycle which comprises; first, bending or forming of a rectilinear staple element into an inverted U shaped staple; second, driving the formed staple out of the tacker; and lastly, the return of both the former and driving blades to their normal elevated positions. Another object is to utilize the forming blade to closely confine the formed staple against play when in the raceway, thus aiding to preclude buckling of the formed staple as it is forced through the raceway, thereby further insuring greater penetration of the driven staple into the material to be secured. Another object is to insure that the foremost staple element of the staple element strip issuing from the cartridge will automatically line itself substantially parallel to the staple raceway prior to the forming operation. More specifically, another object resides in the provision of spring controlled pivoted and slidable pawls for shifting staple element strip forwardly at the conclusion of each cycle of the compound piston. Another object resides in the provision of a novel cartridge of the type referred to for storing thestaple element belt in the form of a roll adapted to be unwound to characterize a staple element strip guided linearly towards the staple raceway of the tacker and in part guided by spaced rails or slotted arms extending forwardly from the bottom wall of the cartridge. Another object comprehends the utilization of an adequate reservoir in the handle of the tacker or fastener ejecting embodiments herein disclosed having sufiicient capacity at all times to contain at least a high pressure pneumatic charge or volume appropriate to operate the forming piston and thereafter the staple driving piston during the first half of a complete operating cycle, that is, the volume of the reservoir is at least equal to the volume of air required to actuate the forming piston and thereafter also efiectively adequate to operate the staple driving piston on the same down stroke of the compound piston herein described and of course, such action is independent of the length of the hose connection to the handle or independent of involuntary cross sectional reduction of the hose in case. the latter be kinked, or even independent of restrictions for any reason in regard to normal predetermined volume of air required to flow into the handle. A further object is to provide a pneumatic cylinder wherein the compound piston which embodies a forming piston and a driving piston nested within and guided by the forming piston, is tiltahle relative to the bore of the cylinder and consequently self alining to compensate for the uncontrollable manufacturing tolerances in the parts constituting guide means for the former blade carried by the forming piston and the driver blade carried by the driving piston. Another object resides in the provision of a pneumatic tacker characterized by, a cylinder for carrying the compound piston of the character referred to, a base for guiding a spring controlled reciprocable staple element bending block, and a housing secured to the cylinder and swingably carrying the base, the arrangement being such that the staple element belt carrying cartridge is removably seated on and in part concealed by the housing, and a resilient strap is employed to hold the cartridge on and against the housing. More particularly, another object is to provide spring controlled staple element swingable and slidable feeding pawls permanently associated with the disposable cartridge to facilitate loading thereof as a unit in the tacker. A further object resides in the utilization of a slidable latch carried by the swingable base for interlocking with fixed keeper means secured to the housing. Another object: is concerned with the provision of means for automatically disconnecting the resilient strap from the swingable base upon unlocking the slidable latch from the keeper means and pursuant to swingable displacement of the base out of the housing. Another important object is to utilize the slidable latch for automatically feeding the staple element strip to present the foremost element thereof across the raceway upon completion of the closing of the base when swung into the housing of the tacker. A further object is to prevent the staple element strip from shifting rearwardly when the foremost staple element thereof is formed into a staple and subsequently driven out of the tacker. Another object is realized in the provision of a case or base having a slidably guided bending block shiftable relative to a carrier of the base and including pin means responsive on the down stroke of the former blade and driving blade to actuate the pivoted staple element belt feeding pawls against the resistance 'of appropriate spring means which automatically retracts the feeding pawls on the completion of the return of both the former and driving blades ,to .shift the staple element strip bodily forwardly against stop means in alinement with and above although contiguous to the staple raceway whereby the foremost staple element of the staple strip is supported by the anvil portions traversing the staple raceway. Other important advantages, features and salient aspects of the invention will appear from the following detailed specifications considered in the light of the accompanying drawings wherein:

Fig. 1 is a side elevational view of the pneumatic tacker according to my invention and partly broken away to illustrate the internal construction.

Fig.2 is a front elevational view of Fig. 1.

Fig. 3 is a vertical sectional view on the line 3-3 of Fig. 2, illustrating the staple element forming and driving means in a neutral or fully raised position at which time the compressed air intake port is closed and the exhaust ports are open to the atmosphere.

Fig. 4 is a view substantially similar to Fig. 3 but showing the intake port open, the staple element forming means partly depressed, and the staple driving means still in its neutral or fully raised position.

Fig. 5 is a view substantially similar to Fig. 4, however, depicting the staple forming means'fully depressed and the staple driving means about to move downwardly to drive the formed staple out of the staple guideway.

Fig. 5A is a section along the line SA-SA of Fig. 5 primarily to illustrate how the formed staple issupported and prevented from buckling even towards the completion of the down stroke of the staple driving blade.

Fig. 5B is a fragmentary enlarged view of Fig. 5 but showing the driving blade meeting the formed staple..

Fig. 6 is a view similar to Fig. 5 showing the staple driving means fully depressed and ejecting the formed staple.

Fig. 6A is a fragmentary perspective view of Fig. 6, on a smaller scale and illustrating the formed staple fully ejected.

Fig. 6B is a sectional view on the line 6B6B of Fig. 6.

Fig. 7 is a transverse sectional view on the line 7-7 of'Fig. 3.

Fig. 8 is a fragmentary view of Fig. 5 illustrating the pivoted base or swing case unlocked from the keeper and swung downwardly and away from the front end of the housing to which the keeper is secured.

Fig. 9 is a plan viewof the swingable base or bending block guide taken on the line 9-9 of Fig. 8.

Fig. 10 is a transverse sectional view on the line 1010 pf Fig. 4 to illustrate the locating block for the slidable atc Fig. 11 is a. horizontal sectional view on the line 11-11 of Fig. 3 illustrating the bendingblock guide or base looked against downward pivotal displacement.

Fig. 12 is a view similar to Fig. 11 illustrating the latch shifted rearwardly to unlock the'basefrornthe housing at which time the bending block guide has been shifted rearwardly by the slidable latch, which action causes the staple element belt feeding means to be swung rearwardly.

Fig. 13 is a horizontal sectional view on the bent line 13-13 of Fig. 3.

Fig. 14 is a horizontal sectional view on the line 1414 of Fig. 3.

' Fig. 15 is a horizontal sectional'viewon the line 15--15 of Fig. 8 illustrating the staple element strip feeding pawls alined for successively feeding the foremost staple elements of the staple element strip parallel to the staple element raceway.

Fig. 16 is a sectional view illustrating the feeding pawls out of alinement but adapted automatically 'to shift or twist the staple element belt to present the foremost staple element thereof parallel to the staple element raceway defined by the former and spaced front faces of the fixed staple element strip support.

Fig. 17 is a fragmentary perspective view illustrating the foremost staple element formed over and against the anvil heads or front portions of the slidable bending block to characterize an inverted U-shaped staple.

Fig. 18 is a perspective view of the swingable base, illustrating primarily the outside carrier and its fixed staple element strip guide.

Fig. 19 is a positive view of the elastic and flexible staple element belt formed into a roll and illustrating a part of this roll, namely, the staple element strip, unwound but adapted to be threaded into spaced guide rails of the disposable belt carrying cartridge.

Fig. 19A is an enlarged side elevational view on the line 19A-19A of Fig. 19.

Fig. 20 is an exploded perspective view of the housing or sheath, swingable base or swing case, the staple belt carrying cartridge, the staple element belt feeding means and inter alia, the slidable latch for interlocking with the keeper to hold the base closed and for actuating the belt feeding means when unlocked from the keeper when the base is closed.

Fig. 20A is a fragmentary and enlarged view of the latch illustrated in Fig. 20.

Fig. 21 is a fragmentary view of Fig. 1 on a smaller scale, showing the swingable base-or swing case swung out of the major part of the housing sheath and about ready to automatically release the leaf spring holding the staple element belt cartridge in part within this housing.

Fig. 22 is a view illustrating the swingable staple element belt feeding means about to be displaced rearwardly by the actuating pin of the slidable bending block.

Fig. 23 is an enlarged fragmentary view of Fig. 22 illustrating the biased relation of the pivoted staple element gripping or braking pawl, shown slightly projecting above the staple element belt guide or support when the latter is not supporting a staple element strip.

Fig. 24 is an enlarged fragmentary view of Fig. 22 illustrating the braking pawl wedging against the staple element strip to preclude its rearward displacement in its guide channel.

Fig. 24A is a side elevational view of the tacker on a smaller scale showing the oblique angle made by the cylinder and the swingable base when the latter is held locked within the housing by the latch and this view also illustrates the front nose of the tacker disposed in a corner where fastening by a staple is desired.

Fig. 25 is a sectional view on the line 25-25 of Fig. 5.

Fig. 26 is a sectionalview takenon the bent --line 2626 of Fig. 3. I

Fig. 27 is a fragmentary view on the line 27-27-0f Fig. 4 and shown partly broken away.

Fig. 28 is an enlarged perspective view "illustrating the position of the foremost staple element-of the staple element strip against the rear stop face of thefchannel shaped guide and about to be bent over the anvil heads of the slidable bending block.

Fig. 29 is a sectional iew onthe= line 29-=29-of Fig; '6

Fig. 31 is an enlarged sectional view on the line 31-31 of Fig. 6 illustrating the spaced fingers of the gripping pawl braking the staple element strip.

Fig. 32 is a sectional view substantially on the line 3232 of Fig. 3, to illustrate the centrally arranged relief slot in the casting and its reduced portions.

Fig. 33 is a sectional view on the line 33-33 of Fig. 3 to show guideway for former and driving blades.

Fig. 34 is a sectional view on the bent line 3434 of Fig. 11 showing the manner in which the impact by the carrier on the slidable latch on each down stroke of the compound piston is absorbed by the keeper, to avoid accidental opening of the swingable base.

Fig. 35 is a fragmentary perspective view of the casting or forming piston guiding cylinder.

Fig. 36 is a fragmentary perspective view of the staple element belt cartridge and its swingable and slidably guided staple element strip feeding pawls carrying a looped spring adapted to be energized or tensioned by the cartridge.

Fig. 37 is a sectional view on the line 37-37 of Fig. 3.

Fig. 38 is a perspective view of the staple element belt cartridge permanently carrying the spring controlled staple element strip feeding pawls.

Fig. 39 is a side elevational view of a slightly modified pneumatic tacker according to my invention but depicting the staple element feeding pawls permanently carried by the depending bearing of the casting instead of the staple element belt cartridge.

Fig. 40 is a fragmentary perspective view on a larger scale of the casting shown in Fig. 39 and illustrating the swingable and slidable staple element strip feeding means secured to the depending bearing of the casting or cylindrical casing, and

Fig. 41 is a fragmentary but enlarged view of Fig. 39, showing parts broken away to illustrate staple element strip feeding means carried by the casting.

Fig. 42 is a sectional view on the line 42-42 of Fig. 41, and

Fig. 43 is a fragmentary perspective view of a slightly modified cartridge.

Illustrative of the embodiments disclosed, the pneumatic tacker is generally designated PT and comprises a hollow substantially cylindrical casting C, a swingable base or case CC, and a housing HS secured to casting or casing C and pivotally holding base CC. Housing HS is characterized by the U-shaped sheath S having welded thereto the channel shaped member CH to form guideway PG for the staple element forming blade or former F and the staple driving blade DB (Fig. 3) which is slidably guided between the inwardly turned ends or ears EF of former F (Fig. 28), and between the posterior surfaces PS of the former F and the front surfaces FS of web W of the fixed channel member CH to form a raceway or gap RW adapted to closely receive an inverted U-shaped staple SP, that is, after having been formed its rectilinear wire element E. Forming blade F (Fig. 3) is secured by rivets 10 to extension 11 depending from hollow substantially cylindrical staple forming piston FP slidably guided by bore B of cylinder or casing C.

Rivets 12 anchor driving blade DB to depending extension 13 of the substantially cylindrical staple driving piston SDP slidably guided in the substantially cylindrical cup shaped forming piston FP. Forming a part of driving piston SDP is the. fixed rubber sealing cup 28. Forming piston PP and the staple driving piston SDP for purposes of description may be considered as a compound piston controlled by a pivoted finger operable trigger T adapted to actuate plunger 14 of the valve generally designated V. Plunger 14 is slidably guided in bore 15 of the insert 16 interrupted by ports 17 and 18 respectively. Rod 19 is secured to plunger 14 and fixedly carries the upper poppet member 20 adapted to open or close port 21 (Fig. 5). Plunger 14 and poppet member 20 together with rod 19 may be considered as the valve stem which is self closing, that is, it closes by air pressure on poppet member 20 after finger pressure is removed from the trigger T. Consequently poppet member 20 is normally against seat 22 (Fig. 3) preventing admission of compressed air into bore B from the intake chamber 23 of .handle H which integrally is merged with cylindrical casing C. Also at this time plunger 14 has been forced away by air pressure from outlet or exhaust ports 18 and therefore the latter are in communication with the outlet exhaust chamber 24 of handle H which embodies baflie 25 effectively separating the air intake chamber 23 from the air exhaust chamber 24. It follows that normally intake port 21 is closed and the exhaust ports 18 are open.

Effectively held by the removable cap 26 for casing or cylinder C is the stem 27 which appropriately carries the frustro conical rubber sealing cup 28 which is held in set position relative to cylinder C and which is adapted to be received by cylindrical bore '29 of the staple forming piston FP. Concerning housing HS, specifically sheath S thereof is U-shaped having its front wall 30 (Figs. 1, 2, 28 and 37) indented to define web 31, which at its lower part is interrupted by the spaced slots 32 for receiving the spaced cam shaped lips L at the forward ends of the spaced sides 33 of the slidably guided U-shaped staple element bending block BB which is slidably guided between the spaced sides 34 of the staple element strip support broadly designated BS fitting between and appropriately welded to the spaced sides 35 of the U-shaped shoe or carrier CR.

With staple element strip support BS between and welded to the spaced sides 35 of the carrier CR and the slidable bending block BB arranged between the spaced sides 34 of the latter, latch LT (Fig. 34) is inserted into the substantially horizontally alined slots 36, 37 and 38 in the spaced sides 35 of the carrier CR, the spaced sides 34 of the strip support BS and the spaced sides 33 of the slidable bending block BB. Also note Figs. 10 and 11.

Thereafter metal latch locating block 39 is positioned so that its non circular opening 40 receives middle lug 41 of latch LT to be confined with play between spaced sides 33 (Fig. 34) of the bending block BB, thus locating the latch against withdrawal, although permitting slight lateral displacement of the latch.

Surrounding lug 41 (Fig. 12) of latch LT and abutting block 39 is the helicoidal spring 42 having its outer end encircling projection 43 extending forwardly from the fixed block or stop 44 which includes projection 45 (Figs. 25 and 29) arranged in opening 46 in the bottom wall of carrier CR. Block 44 is held by latch spring 42 against the rear wall of opening 46 (Figs. 5 and 30) and against fulcrum pin 47 fixedly retained in the alined and spaced perforations of ears 48 and 49 of the spaced arms 50 extending from sheath S and the depending sides 51 of the keeper K. It will be observed that sides 51 of keeper K are interconnected by a bridge 52 'constituting a seat for the split staple element belt cartridge or container generally denoted SBC. It will also be observed that block 44 is held against upward displacement by the rear ledges 34A overhanging the spaced sides 34 of the staple element support BS, that is, these ledges act on the upper part of block 44 to, hold the lower shoulders 44H thereof against the bottom wall 98 of the carrier or guide CR. 1

Helicoidalf's'pring 42 acts 'to normally urge the'forwardly projecting limbs 53 of latch LT against alined front faces of-the longitudinally arranged slots" 36 and 37 of the carrier CR and staple element strip support BS, respectively. 'Attention, however, is directedto-the fact that the laterally extending lobes 54 of latch 'LT are slightly tapered-and overhang the spaced sides (Figs. 26 and 34) ofthe carrier CR and are adapted to ride onto upwardly and forwardly inclined faces 55 of the alinednotches N interrupting the forward parts of the spaced sides 51 of keeper K. 'Ihese notchesN also communicate with alined 'relief're'cesses 56. Stated in another way, the forward parts of spaced sides 51 of the keeper K characterize hook shaped portions of noses 57 adapted to 'removablyinterlock with the laterally extending lobes 54 of theslidably guided latch LT which has its limbs '53 abutting the front end faces of slots 36 and 37 of carrier CR and staple element strip support BS, in the event lobes 54 are out of the alined notches N and their respective communicating recesses 56 (Fig. 8), that is, when the base CC is unlocked from housing HS.

Where, however, the tapered lobes 54 are interlocked with the walls of notches N, limbs 53 'of the latch LT are slightly spaced from the front end walls of the alined slots 36 and 37 and even from the front'end wall of the alined notches N of the keeper as clearly shown in Fig. 11.

7 Attention is now directedto the elastic, flexible and foldable staple element belt SE adapted to be closely wound upon itself in the form of roll R (Fig. 19). Broadly speaking, this belt consists ofrectilinear and juxtapositioned elements of suitable steel wire resiliently connected by the elastic coating 60' (Fig. 19A) reinforced if desired by the relatively thin and elastic transparent film or tape TP. R011 R is positioned within a split container or cartridge SBC, preferably of a suitable plastic material and if desired transparent. As illustrated cartridge SBC (Figs. 3, 20-and 38) comprises complementary parts generally indicated 61 and 62 having annular rims 63 and 64 each interrupted at their lower parts by a gap or throat as 65 (Figs. 3, 4 and 20) communicating with slots 66 and 67 defined by staple element guide rails 68-and 69 of the spaced wings 70 and 71 (Fig. 20). -More specifically, rails 68 and 69 may be considered as constituted by spaced upper and lower parallel walls 72 and73, the upper walls also merging with its associated annular rim. as is well understood. Integral with complements 61 and 62 are as ears or arms 74 each having an overhanging fulcrum pin or post 76. Rims 63 and have their inner margins appropriately rabbeted to'provide reduced and intcrfitting portions 75 and 75' (Figs. 10, 14, 20 and 37) adapted to be glued together after insertion of the staple element roll R.

Also integral with complementary parts 61 and 62 of the staple element cartridge SBC are the laterally extending rearwardly inclined fins or ribs FN having front fiat faces 77 adapted to abut the stop faces 78 of the upstanding and spaced wings-or extensions 79 integral with but outwardly offset from the spaced sides or arms 50 of sheath S.

Fulcrum posts 76015 the disposal cartridge swingably carry a pair of pawls P each having an arm 80 merged at its lower end with a laterally arranged extension 81 each provided with aforwardly projecting finger 82 embodying at its forward end a rounded staple element gripping tooth or projection 83. Fingers 82 each include a rearwardly'flared portion characterized also by downwardly and rearwardlyextending cam face 84.

-Each arm-80 ofthe-pawls is provided with an inwardly turnedand bent flange85 having spaced studs 86 (Fig. 20) against which the anterior spaced legs '87- of the-leaf spring generally indicated 88 is appropriately welded in which case studs 86 will'melt into its respective spring legs and associated leg support. This spring 88 is bent intermediate legs 87 to form a loop LL (Fig. 22) and v has its rear portion 89 which includes bridge 90 interconnecting legs 87 which are adapted to abutthe removable cartridge SBC. However it should be observed that arms 80 of the pawls P each'embody an elongated slot 91 fitting over a fulcrum post 76 of the complementaryparts 61 and 62 of the cartridge. With legs 87 of spring 88 welded to bent flanges 85 of the pawls P and the latter arranged on' posts 16 and with the rear part 89 of spring 88 abutting the complementary circular rims of the cartridge 'SBC (Fig. 38), the pawls P, that is, the'arms 80 thereof are prevented from accidentalremoval from posts 76 in that legs 87 of spring 88 closely straddle flanges 80. By the construction disclosed pawls P have a loose slidable and swingable connection with the cartridge and additionally are eifectively retained thereon. It is evident therefore that pawls P may be pivoted and slidably displaced relative to the cartridge SBC. Normally legs 87 of the U-shaped and bent spring 88 slope downwardly and forwardly following the direction of the contour of flange 85 of the pawls P. Of importance it should be realized that legs 87 are reduced at their lower ends to characterize terminal fingers 92.

' Thesefingers 92 of spring 88 characterize means in association'with teeth or convexed projections 83 of the pawls P to grip staple strip SE and shift the latter forwardly, that is, towards raceway RW after a complete cycle of the compound piston, that is, upon complete return stroke of the forming and driving blades F and DB, namely, to their normally raised position illustrated in Fig. 3.

The staple element strip SE issuing from the staple element belt R is gripped against rearward shifting by the tiltable and normally biased braking block GB (Fig. 5, 6, 20, 26, 31 and 37) which comprises reduced portion 93 (Fig. 31) loosely disposed in slot 94 in bottom wall 95 of U-shaped bending block BB. Depending from reduced portion 93 is the projection 96 which is loosely disposed in opening 97 in the bottom wall 98 of the U shaped carrier or carriage CR, the arrangement being such that shoulders 99 are tiltable or rockable relative to bottom wall 98 of carrier CR. It is also apparent that sheath S has its lower part offset or reduced with respect to its upper part, to Wit, its spaced arms 50 are a distance apart greater than the distance between its spaced extensions 79 although interconnected by the curved shoulders 100, thus providing spaced compartments CM (Fig. 31) for convenient reception of the spaced rails or guides 68 and 69 of the split cartridge SBC.

Brake or grab pawl GB embodies at its upper part the spaced fingers 101 (Figs. 31 and 37) for coacting with the lower faces of the staple element strip SE slidably disposed within the slotted rails or arms '68 and 69 of the cartridge components 61 and '62. An intermediate reduced part or tongue 93' (Figs. 18, 20 and 31) of bridge 93 of the staple strip support BS is straddled by the spaced fingers 101 and received Within-recess 102 at the upper part of pawl GB. Also fingers 101 movably fit into the spaced and alined notches 103 interrupting bridge or staple element seat 93. Even the rear and uppermost corners 101 (Fig. 23) extends slightly above the upper surface of seat 93 when the base CC is unlocked and swung downwardly out of the keeper K and sheath S (Figs. 8 and 21), sheath S constituting the housing HS for the swingable base CC.

Gripping pawl or staple element brake GB and the rear upstanding lug 104 of bending block BB areappropriately interconnected by helicoidal, spring 105. .Specifically the front end or eye 106 of this spring is retained on lug orhook 107 extending from pawl GB while its reareye -108.isheld on lug 104. This. spring 105v has adouble function,- znamely, one, --to normally huge the pivoted pawl PG rearwardly, and two, to urge the staple element bending block BB in a forward direction to present the spaced lips L of the spaced sides 33 through the spaced gaps 32 of web 31, and of course at a time when both the staple former F and the driving blade BB are above these lips L (Fig. 3) at which time the front end of the bottom wall 95 of bending block BB abuts web 31 of the indented wall 30 thus limiting further forward movement of block BB. Thus if the compound piston is in its normally raised position and awaiting. finger manipulation of pivoted trigger T, lips or cams L extend through the vertical former guideway PG and even project outside of sheath S. Lips L continue'to project across guideway FG on the down stroke of the former F until ends EN (Fig. 28) of the foremost element E of p the staple strip SE are bent against the outside side walls 200 of the spaced anvil heads AH to form the inverted U-shaped staple SP. After the latter is completely formed and with its depending legs straddling the anvil heads AH, the front wall oftheformer F (Fig. 6) meets lips L causing the bending block BB to recede or slidably shift rearwardly against the resistance of spring 105.

When base CC is swung into the fixed keeper K carried by sheath S, seat 52 for supporting cartridge SBC is positioned on spaced and alined lugs 114 and against alined vertical shoulder 115 of the spaced sides 35 of carrier CR. Projections or anvil heads AH of spaced sides 33 of the slidable bending block BB movably extend into relief gaps 118 (Figs. 9, 17, 18 and 20) interrupting the front end FE of bridge 93 of the staple element support 93.

Concerning the staple element bending or shaping anvil block BB, it will be noted that the spaced side walls 33 carry fixed pin 110 which has its ends projecting into the alined elongated slots 111 near the front end of the spaced sides 34 to permit the anvil block BB to slide lengthwise relative to support BS and carrier CR. The ends of this pin 110 also extend beyond the overhanging spaced side walls 34 of the staple strip support BS and into alined relief recess 117 interrupting spaced sides 35 of carrier CR.

On the down stroke of the forming blade F, spaced lips L are cammed to cause bending block BB to slide rearwardly relative to the carrier CR. If the bending block BB is moved rearwardly, helicoidal spring 195 is extended, consequently, braking the tiltable pawl GB (Figs. 22 and 24) which is also urged slightly rearwardly and positively grips the staple element strip SE against the downwardly and forwardly disposed platen 112 (Fig. which is integral with and extends rearwardly from web W (Figs. 5 and 28) of channeled shaped member CH welded to the front wall 30 of the sheath S. In fact platen 112 together with staple element strip seat 93 constitutes a forwardly and downwardly inclined channel 113 for directing the staple element strip SE towards guideway FG formed in part by the indented front wall 30 of sheath S and channel shaped member CH, and, also by wall 30 of sheath S and by front Walls 144) of spaced sides 34 of support BS.

Platen 112. together with the spaced support 93 characterizing channel 113 and may be said to constitute a chute for the staple element strip SE, that is, in directing the latter towards and the foremost staple element thereof into raceway RW and under former F. More particularly, this channel 113 together with the guide slots 66 and 67 o-fthe guide rails 68 and 69 of the staple element container or cartridge SBC direct the staple element strip to wards the front raceway RW.

Referring to Figs. 13 and 35 and to the cylindrical casting C, the latter embodies the reduced portion 115 having fiat side 1116 straddled by extensions 79 of sheath S removably secured to this reduced portion or boss 115' by screws 117. Integral with and depending from reduced portion 115' is the channel shaped bearing 118 having laterally extending flanges 119 (Figs. 32 and 33) 16 contiguous to web W of the channel shaped member CH welded to sheath S.

Integral with and extending rearwardly from reduced portion or boss of the cylindrical casting C are the spaced lugs fixedly carrying the hollow fulcrum pin 131 (Fig. 6) about which is the rotatable loop 132 to which the upper end of retaining leaf spring strap ST is anchored by rivets 133. Incidentally loop 132 is desirably loosely disposed about pin 131 to permit strap ST to lie flat against the cartridge. This strap ST is utilized to'hold staple element cartridge SEC on seat 52 and the inclined faces 77 of the inclined fins FN against the rear faces 78 of extensions 79 of sheath S at which time the staple element guide rails 68 and 69 (Fig. 15) extend deep into sheath S positioning the spaced spring controlled swingable feeding pawls P near the front end of the staple element strip SE, that is, near the foremost staple of this strip (Fig. 22). Also at this time the upper front part of the cartridge SBC is in the relief arcuate recess AR interrupting reduced boss 115 of the casting (Figs. .1, 3 and 35). If strap ST be unhooked from the carriage CR, that is, from its rear perforated wall 136, this spring,.due to its own resiliency flattens out asindicated by the dash and dot lines in Fig. 3. It follows that if the stapleelement belt be used up, it may be quickly replaced by a new cartridge, which can be promptly mounted on seat 52 to position fins FN thereof against stop faces 78 of sheath S, thereby arranging its spaced rails in spaced compartments CM. and hence these rails or guides 68 and 69 widely straddle the staple element strip seat 93 and platen 112.. Subsequently strap ST is swung to permit entry of lip or hook 134 into opening 135 to interlock with wall or bridge 136 of the outside carrier CR. This can only take place when base CC is u-nlatched from and swung out of the housing. Thereafter base CC is swung to its closed position to permit latch LT to interlock with keeper K. By this action strap ST becomes tightly wrapped about the cartridge with fins FN firmly against stop faces78. By positioning the cartridge within housing HS, that is, on seat 52, stop faces 78 cooperating with fins FN limit forward displacement of the cartridge; outside and spaced surfaces 301 (Figs. 20, 37 and 38) of the rear part. of arms 74 cooperate with the inside faces of the spaced extensions or wings 79 of sheath S to limit lateral displacement of the cartridge while the taut strap ST after interlocking with bridge 136 and after fully closing of the swingable base CC, holds the cartridge against rearward displacement, and consequently in its located and set position on seat 52., at which time extensions 81 of pawls P yieldingly abut front projections or lugs 81A of keeper K (Figs. 8, 20 and 26) to position pawls P in the machine and limit forward displacement thereof.

Strap ST will disengage from the cartridge automatically when latch LT is shifted rearwardly to unlock from keeper K and if thereafter base CC is swung out fully from the housing HS in which instance access may be had to the parts forming guideway PG and raceway RW formed by sheath S and base CC.

More specifically, fulcrum pin 47 goes through the perforated ears 48 and 49 of sheath S and keeper K. This pin also goes through spaced and perforated ears 137 at the rear part of carrier CR. Fulcrum pin 47 is effectively retained set by snap C rings as 138. By this arrangement, the base CC (Fig. 21) which comprises staple element strip support BS, the slidable bending block BB, slidable latch LT, braking pawl GB and other operating parts associated with the carrier CR, may be swung into or out of the housing HS defined by sheath S and its inside fixed keeper K. In Fig. 21, base CC is illustrated as unlocked from housing HS and almost fully swung out of the latter. By such action, .hook 134 is about ready to automatically detach from bridge 136. On further rearward swingable displacement of base CC,- hook 134 does in fact automatically disengagefrom bridge 136 and immediately assumes the straight and flat position as previously referred to and as illustrated in the dash and dot lines in Fig. 3. The cartridge is thus free to be removed from the housing, and more specifically from seat 52 of keeper K and of course from between the spaced extensions 79 of sheath S. Manifestlythe spaced and pivoted staple element feeding pawls P since they are permanently associated with cartridge SBC in the embodiment shown in Figs. 1-38, likewise are withdrawn from between extensions 79. In other words, the cartridge SBC which carries the feeding pawls P, may be withdrawn, discarded and replaced .by' a fully loaded cartridge which likewise carries its own pair of staple element feeding pawls.

When base CC is unlocked and swung out of housing HS, pin 110 which overhangs sides 34 of the staple belt supporting member BS is at the forward ends of the alined slots 111 of the spaced sides 34 of the staple strip support BS due to the action of helicoidal spring 105 which always tends to urge bending block BB forwardly (Fig. 8) wherebyanvil or shaping heads AH of this bending or shaping block extend beyond the forward end FE of tongue or seat 93 (Fig. 9). r stated in another way, the anvil heads AH, extend beyond the inclined but alined guide faces 140 of the spaced sides 34 at the front ends of the staple element support BS whose sides 34 terminating in spaced feet 141 receivably in positioning and spaced notches 142 (Fig. 20) interrupting carrier CR. In other words, feet 141 straddle tongue 143 at the front part of bottom wall 144 of the U-shaped carrier CR.

Also when base CC is unlocked and swung out of housing HS, lobes 54 of latch LT are at their most forward position relative to alined slots 36 of the spaced sides 35 of carrier CR due to the action of spring 42 which always has the tendency to urge block 39 forwardly and since block 39 abuts web 145 of latch LT, the slightly tapered lobes 54 of legs 53 abut the forward ends of slots 36. However, after the housing HS has been loaded with a new cartridge SBC, and base CC is swung towards the housing HS, lips 54 meet and contact the spaced inclined cams 57 of keeper K thereby causing bodily rearward displacement of latch LT until these lips 54 reach and pass over the apices of the spaced cams 57. Thereafter spring 42 automatically shifts latch LT forwardly to ride along cam faces 55 and into notches N, stopping just short of the forward end faces of alined slots 36 and 37 (Fig. 11) at which time intermediate portions 146 interconnecting web 145 and outside wings 147 of latch LT are disposed within the alined clearing recesses 148 and 149 in the spaced sides 50 of sheath S and spaced sides 51 of the keeper K respectively at which time outside wings 147 and the spaced actuating lugs 150 of latch LT straddle the secured ears 48 and 49 of the housing HS, that is, the sheath S and keeper K thereof at the rear part of the housing, while as front part of the housing, sides 50 and 51 of sheath S and its secured keeper K are arranged in notches 151 defined by Wings 147 and spaced limbs 53.

According to the invention latch LT has adequate play or clearance 400 (Fig. 34) between the locating block 39 and the spaced sides 33 of the U-shaped bending block BB. This play permits rotational displacement of latch LT relative to housing HS. Advantage is taken of this rotational displacement to permit latch LT to properly aline itself at the completion of its locking engagement with keeper K, that is, with walls of notches N. For example, in actual practice, cam faces 55 of notches N of keeper K may not be at the same elevation. Hence onev of the lobes 54 of latch LT would completely be in its home position in advance of its companion but opposite lobe 54 which at this time should cooperate with the other side of the keeper but because of differential or manufacturing tolerances is not in its complete home position. In such case, spring 42 acting on locating block SQFautOmaticaIIy causes the block to compensate for such differential tolerance, and thus rotates slightly, thereby'causing the latch to correspondingly rotate whereby the lobe 54 'of latch LT, previously not in its complete home position, to effectively rotate into such position and of course automatically. In other words, latch LT is self alining to permit both of its lobes to completely and effectively interlock with the walls of respective notches N even though the lower and spaced cam surfaces 55 thereof may be at different elevations due to involuntary tolerances occurring in actual practice.

To open housing HS, the tapered wings 147 are grasped by the operator and shifted-rearwardly. This action cornpresses spring 42 and eventually the spaced actuating lugs 150 of latch LT, strike the rear ends 152 (Figs. 11 and 12) of the alined slots 38 in the spaced sides 33 of bending block BB. Consequently this U -shaped bending block is slidably guided rearwardly and to a position where lobes 54 of legs 53 of latch LT are out of alined notches N, that is, free of the apices of cams 57 and are arranged in clearing recess 56, thus unlocking latch LT from keeper K, permitting base CC to be swung downwardly and rearwardly out of the keeper K to automatically unlock strap ST from carrier CR whereby the staple element cartridge SBC may be withdrawn from the housing-HS and replaced if desired.

Specially referring to Figs. 20, 29, 30 and 30A, it will be noted that the spaced sides 33 of bending block'BB are provided with notches as 44A to characterize reduced portions 44B slidably receivable in vertical gaps 44C (Figs. 29, 30 and 30A) defined by the inner faces 44D of the spaced sides 34 and the spaced side faces 44E of the fixed block 44 wherein shoulders 44F (Fig. 29) are spaced from bottom wall 98 of carrier CR to also slidably guide the reciprocable bending block BB. By this arrangement the rear parts 448 of the bending block BB movably project into relief gaps 44C on the down stroke of the former F and also on the down stroke of the driving blade DB but slide out of the gaps 44C upon com pletion of the return stroke of both the former and driving blades.

Attention is again called to the fact that guideway FG is formed at its upper part by web 31 of sheath S and web W of the channel shaped member CH (Figs. 3, 28 and 33) and at its lower part by Web 31 of sheath S and by the spaced faces of the staple element support BS. In the assembled relation of housing HS and cylinder C, flanges 119 of bearing.118 are against web W (Fig. 33) while the tapered and externally convex terminal 500 of cylinder C is against the front wall 30 of sheath S. In other words, terminal 500 together with depending bearing 118 define a gap 591 (Figs. 3, 32 and 35) for closely receiving the upper part of housing HS characterized by sheath S and its secured channel shaped member CH. However the cylinder C is provided between shoulder 156 and inner upper face 503 (Fig. 3) of terminal500 with relief slot 502 (Figs. 3, S and 32) to preclude interference with the former and driving blades F and DB during displacement thereof.

Due to manufacturing tolerances slight misalinement may take place between sheath S and channel shaped member CH relative to bore B of cylinder C and in ac-' cordance with the invention herein disclosed, in the event uncontrollable tolerances exist causing such misalinement, the latter is compensated for by permitting the forming piston F? to tilt slightly without losing the etfective seal thereof. To this end it will be observed that forming piston FP embodies the laterally extending circumferential rib 600 to which rubber ring 601 is appropriately fixed. This ring coacts to seal and pivotally bear against the cylindrical wall bore B. By such construction the forming piston and fortuitously the staple driving piston may rock or swing slightly relative to the cylinder in the event of misalinement between the wall of bore B in regard to the sheath Sand web W which constitute the upper part of guideway' FG" and"in"regard to sheath S together with spaced faces 140 of the stapleelement support BS which constitute the lower part of track or guideway FG. It should be noted that rib 600 has external converging faces interrupted by a gap as illustrated for adequately retaining rubber ring 601.

Coming now to the staple element cartridge SBC (Figs. and the lower walls 72 and 73 of the staple element guide rails 68 and 69 are each provided with a notch 700 (Figs. 15, 20 and 37) and the lower walls embody effective interfitting rabbeted margins 75 and 75'. Consequently in the assembled relation of components 61 and 62 the latter defines recess 701 (Figs. 15' and 37) to clear platen 112 and staple element seat 93 as is well understood.

In Fig. 3, the pneumatic tacker PT is shown in a neutral position, that is, both the forming piston PP and staple driving piston SDP are fully elevated and thus both the forming blade F and the driving blade DB are slightly above the foremost straight staple element E, trigger T is held depressed by air pressure on poppet member 20, the intake port 22 is closed, the exhaust ports 18 are open, the staple element strip SE has been threaded through the slotted rails 68 and 69 and into the chute comprising the downwardly sloping platen 112 and the spaced staple element seat or support 93, and of course by the channeled or slotted rails 68 and 69 of cartridge SBC straddling platen 112 and seat 93 and While fins FN of the cartridge are held against sheath S by strap ST. It should be mentioned that forming piston FF is held normally raised by helicoidal spring 155 seated on annular shoulder 156 within lower part of cylinder C. This spring also abuts annular shoulder 157 at the lower part of the forming piston FP. If the operator lifts trigger T, plunger 14 is raised (note Fig. 4), thus closing exhaust ports 18 concomitantly opening intake port 21. Consequently compressed air from chamber 23 flows through ports 17, into the intermediate duct 160 and around the upper end of and into and about the forming piston FP and against the rubber cup 28 carried by stem 27 to seal the latter against the inside cylindrical bore of forcing piston PP.

The forming piston therefore moves downwardly and therefore the former blade F moves against the foremost straight staple element E positioned across and on anvil heads AH of the bending block BB. At this phase of this specification attention is now particularly directed to Fig. 28 wherein only the foremost staple element is shown for purposes of clarity in respect to teaching the automatic control means for locating this foremost staple element, across the anvil heads AH now projecting into guideway or passageway FG. Previously it was specified that the channel shaped member CH which is desirably welded to sheath S in part defines means for guiding the staple former blade F and staple driving blade DB. Of course platen 112 of this channel shaped member CI-I also in part defines the downwardly and forwardly inclined chute or guide means for staple strip SE. In addition wings WW forwardly ofiset relative to web W of this channel shaped member CH serve as stop means for ends EN of the foremost staple element E to limit forward movement of this element at which time the latter is across and supported by the anvil heads AH although the intermediate portion of the element is in alinement with and across raceway RW and under the lowermost part of the inwardly turned ends EF of the former F. These ends EF operate to bend the ends of the foremost staple element against the outside side faces 200 (Figs. 20 and 28) of the anvil heads AH to form the inverted U-shaped staple SP (Fig. 27). This action of the former F takes place on the first part of the down stroke of former piston PP and almost instantly after the trigger T is actuated. On the continuation of the downward stroke of the forming blade or former F the latter meets lips L, causing the bending block or anvil means BB to l4 slide rearwardly. This action stretches spring which causes the gripping block GB to tilt slightly rearwardly as indicated by the dotted lines in Fig. 22 causing corner 101 (Fig. 24) of the spaced fingers 101 to grip and dig against and even slightly tilt a staple element E of the staple stripSE, causing the latter to be pressed against the upper face 113 of platen 112, thus preventing this belt from backing up or shifting rearwardly away from guideway or passageway FG. On the same down stroke of the former but after staple element E has been bent into the inverted U-shaped staple SP another important function takes place apart from braking the staple element strip SE, that is, former F meets the cams or lips L of the bending block BB. Therefore as-previously stated the bending block is slidably and rearwardly displaced and consequently the fixed pin bodily carried by the bending block is correspondingly shifted rearwardly. If block BB is shifted by former F, the anvil heads AH start to recede into spaced relief slots 118, that is, move rearwardly in a direction away from the formed staple now in guideway FG and on the down stroke of the driving blade DB, anvil heads AH completely clear raceway RW in a manner hereinafter more specifically discussed.

It has been stated pin 110 bodily moves rearwardly with the bending block or anvil member BB. Eventually the former blade F moves further downwardly carrying with it the formed staple SP and the ends of pin 110 meet the alined cam faces 84 of pawls P, causing these pawls P to swing rearwardly and slightly upwardly by reason of the loose but pivoted connections defined by posts 76 of the forwardly projecting spaced arms 74 on cartridge components 61 and 62, and the elongated slots 91 on pawls P as indicated by the broken lines in Fig. 22. Spring fingers 92 of arms 87 of the U-shaped spring 88 thus release their grip on the staple strip SE on the down stroke of former F.

On this down stroke of former F, the formed staple SP meets lips L which have their forward portions still traversing staple raceway RW (Fig. 5) but at a time when pin 110 is almost at the rear part of slots 111. At this time although staple element feed pawls P have re'- leased their grip on the staple element belt SE, the formed staple is held by. lips L within the former and against alined and spaced faces of the staple element support BS. But now the former F has completed its full down stroke and consequently spring is almost fully compressed and bears against annular thimble TH surrounding spring 155. In turn, thimble TH compresses the superimposed rubber buffer rings BF which absorb the shock imparted by the forming piston and later by the driving piston and which have a snug fit with the wall of bore B, the lowermost ring BF being retained on annular shoulder 201. It has been assumed that where the former F meets the foremost staple element E still resiliently connected to the staple strip SE, this foremost staple element after its ends EN are bent against faces 200 of lips L by ears or ends EF of the former F, the staple thus formed will be severed by the former from the staple element strip and will be frictionally retained within the former and against the side faces 201 of bent ears EF (Fig. 28) and consequently this formed staple will move bodily downwardly with the former up to its meeting with the spaced cams or lips L at the lower part or the raceway RW (Fig. 5). This condition arises only when the friction between side faces 201 of bent in ears or endsEF and the depending legs of the staple is large enough to cause the formed staple to move bodily with the former in which case the bent staple is severed from the elastic staple element strip SE. In actual practice this generally happens. In instances where-the friction between the formed staple and the former is insufficient, the staple formed against the anvil heads would still be resiliently connected to the staple element strip and would hang in the raceway RW after recession rearward displacement of the anvil heads AH, awaiting the impact by the driving blade DB on its down stroke to sever the now formed staple from the staple element strip SE. This condition likewise often occurs in actual use.

Up to this phase of the cycle of operation, the former F has compl'eted'its full down stroke (Fig. the staple has been formed from the previously foremost staple element E, the staple element feeding pawls P have been rearwardly and upwardly displaced, thus emerging spring arms 87 of spring 88,'spring fingers 92 have released their hold on the staple element strip SE, trigger T is still elevated, the staple driving piston SDP also is fully eleyated, but towards the end of the down stroke of the former piston FP, the latter FP has passed downwardly and away from the frusto conical rubber sealing cup 28 carried by stem 27 of cup 26 of casting or cylinder C. Itfollows that compressed air under maximum predeterminedpressure enters annular port 203 formed by the gap between sealing cup 26 and former piston FF and into the former piston FP, thus actuating driving piston SDP downwardly relative to the former piston FP. Hence driving blade DB moves downward in the blade guideway, that is, between posterior face PS of the former F and the forward face P8 of web W (Fig. 28) and also between the side faces 201 defined by'ears EF of the former. It may be well to mention at this point that blade guiding means RW is formed at its lower part by the front faces 140 of the spaced sides 34 of staple element support BS, the side faces 201 of ears EF of former F and the posterior surface PS of the former and consequently blade guideway RW also forms the staple raceway or staple guideway communicating with'the staple element guide channel 113 for receiving the foremost element of the staple element strip SE.

Where the formed staple has been severed by the former it is supported by lips L across raceway RW (Fig. 6), and the downwardly moving blade DB meets the bridge of this staple. If the formed staple be still con nected to the staple element strip, this formed staple would be severed from the strip by the driver blade DB. In either case, eventually the formed staple becomes seated against spaced lips L which are still across the staple raceway RW (note Fig. 6) before the'complete down stroke of the staple driving blade DB. Suppose a pause is taken to analyze what has actually happened at this phase of the downward stroke of the driving blade DB in respect to the manner of supporting the driven staple towards the completion of the down stroke of blade DB. In this connection attention is directed to Figs. 5A and 5B, wherein the formed staple SP has its bridge 210 seated on spaced lips L and confined between posterior surface PS of former F and the spaced guide faces 140 of the spaced sides 34 of staple element support BS while the spaced legs 211 depending from bridge 210 are confined between sides end faces 201 of ears EF of the former, the outside faces 200 of lips L, spaced guide faces 140 of the staple element support BS and the posterior surface PS of former F at a time when bridge 210 is seated on lips L. In otherwords each of the depending legs of the formed and driven staple is stabilized against play even't'owardsthe completion of the down stroke of the driving blade, that is, prevented from buckling by five surfaces;j PS,'l 201, 14!), 200 and by a cam surface of its respective' and associated lip L and on actual driving by still a sixth surface, namely, bottom surface 212 of the driving blade DB. It follows'that the driven staple is supported all around its legs or' shanks 211' against buckling, enhancing the penetration thereof into the material in which the formedstaple is driven. Of course-at the completion of the stapledriving stroke by blade DB the formcdstaple is ejected'frorn the tacker (Figs. 6 and 6A) at" which time blade DB has displaced lips 'L clear out'of raceway RW and the staple driving piston-has compressed the rubber buffer ring 220 seated '16 within forming piston FF which further compresses the superimposed buffer rings BF (Fig. 6).

At all times after the staple element is bent but during the down stroke of both the former F and driving blade DB, fingers 101 of brake pawl GB coact to prevent rearward displacement of the staple strip SE. Additionally the spring controlled pawls P have swung to the rearmost positions (Fig. 6), such movement being permitted in view of the rearwardly and downwardly inclined relief shoulders 260 '(Figs. 1, 20 and 22) below and to the rear of fulcrum posts 76 on arms 74 of the cartridge SBC.

With the staple expelled, the operator removes finger pressure from the pivoted trigger T. Instantly the valve stem drops due to air pressure on poppet member 20. It follows that intake port 21 closes and exhaust ports 18 open, causing the air within the bore of the former piston FF and within bore B to flow into channel or duct 160 into ports 17 and bore 270 of insert 16, through exhaust ports 18, then into exhaust chamber 24 to the atmosphere, in other words air pressure in and around the former piston has been precipitously removed. By such action spring 155 recoils, that is, expands to elevate former piston FP to its normally or neutral position (Fig. 3). During retraction of the former piston, the staple driving piston SDP is raised likewise to its normal position and during such action lips LL are automatically projected across gap PG and slightly through the spaced openings 32 of front wall 30 of sheath S.

It is remembered that spring arms 87 (Figs. 4, 5, 6 and 22) were energized or placed under tension on the down stroke of the former blade F and blade DB and such spring arms 87 await the return or up stroke of both of these blades, at which time and more particularly when both the former F and the staple driving blade DB have gone beyond the elevation of channel 113 at which time spring arms 87 of spring 88 release their energy, sending feeding pawls P forwardly, hence causing the spaced spring fingers 92 to shift staple element belt SE forwardly in channel 113 to again present the foremost staple of stripSE over anvil heads AH and against stop wings W of the U-shaped channel shaped member CH, bearing in mind of course that by reason of the operating cycle abo've discussed the staple element belt wound up in the form of roll R has been depreciated by one staple element, namely, the discharged staple. Hence on each operating cycle, roll R loses one staple and as is well understood the roll unwinds to issue the staple strip SE from the secured cartridge or containerSBC during operation of the tacker.

Attention is particularly directed at this time to Figs. 36 and 38. It will be observed that the cartridge SBC permanently, swingably and slidably. carries the staple element strip feeding means in the form of-spring controlled and spaced pawls P. If the cartridge be positioned on seat 52 with the spaced fins FN against faces 78 of sheath S, the upper curved parts of components 63 and 64 fit against the curved'portion AR at the rear of the casting C at which time the upper spaced arms 74 which swingably and slidably carry pawls P straddle bearing 118 depending from the reduced portion of the casting or cylinder C. Also the alined lower staple guide rails 68 and 69 which are integral with components 64 and 63 of the cartridge straddle staple element seat 93 and platen 112 (Figure 31). Withpaw'ls P swingably and slidably connected to upper arms 74, the rear intermediate parts 89 of U-shaped spring 88 bears yieldingly againstthe companion rims 63 and 64 of the cartridge, which action normally urges the swingable pawls P forwardly and against stop faces 280, on upper arms 74.

In accordance with the invention the lower margin LM of the'front wall 30 of sheath S as well as proximal depending portions 300 of the spaced sides 50 thereof, extend downward to a level of the lower faces of spaced feet 14-1 of the supportBS, thus defining a marginal shield or nose NZ (Fig. 24A) adapted to be received in a corner 

